In oil and other hydrocarbon production, drilling, completion and workover, fluids are typically circulated down the string of tubes and upwards around the outside of the tubes, contacting the formation surface of the wellbore from which the hydrocarbons are to be produced. In the case of a completion or workover fluids an original clear brine is typically prescribed to have a density which is a function of the formation pressure. The salts and other additives in the completion or workover fluid may be partially diluted by the formation water, as a result of contact with the formation. The brines can also become diluted deliberately by the well operator, who may add water to replace fluid lost into the formation, or to reduce the density following a decision that it is too high. Whatever the reason for an altered density of the fluid, it may be desirable in many instances to use additives to restore or increase density in the completion or workover fluid. Cesium and bromides work well as densifying agents in completion and workover fluids, but they are expensive, and, as with any other material which must ultimately be disposed of, should be recycled to the extent reasonably possible.
This invention is, in one aspect, directed to the recycling of cesium, bromides, and other components in completion and workover fluids, for economic as well as environmental reasons. In much the same manner, drilling fluid components may also be conserved and recycled by the present invention. Common drilling fluid components include weighting or densifying agents such as barium compounds, clays such as bentonite clay, and various natural or synthetic thickeners, all added to assist in the removal of cuttings from the well bore. Ingredients of drilling fluids, also called drilling muds, may be referred to herein as “drilling fluid components.”
As used herein, the term “heavy brine components” means calcium, zinc, ammonium and/or cesium as cations and chloride, formate and particularly bromide as anions from any source. Typical sources include cesium chloride or formate, calcium chloride, sodium chloride, sodium bromide, calcium bromide, zinc chloride, zinc bromide, ammonium chloride, and mixtures thereof as well as their cation and anion forming moieties from other sources.
Many oil well fluids contain polymers added for various purposes including to increase viscosity to help remove solids from the well and to retard the fluid loss into the formation. Polymers may be considered contaminants for various types of recycling, and in any event are difficult to remove, particularly when they are present with substantial quantities of solids.
Oil well muds generally include large proportions of solids, making their disposal difficult; also they contain additives which are beneficially recovered and recycled. Disposal is also difficult for other common oil well fluids such as water/oil (or oil/water) emulsions of widely varying composition including muds; recovering the more valuable components of emulsions for recycling or other use has been very difficult
Not least among the difficulties of dealing with dilute, spent or used oil well fluids is the mundane but expensive task of trucking the fluids from remote producing wells to distant environmentally approved disposal sites or processing plants. Quite apart from the utter waste of materials, the cost of hauling dilute brines and other oil well fluids for disposal is a serious counterproductive burden to the producer. A related point is that if the excess water in dilute fluids is not eliminated or recovered for various purposes, the volume of fluid at the wellsite continues to increase, requiring more and more additives to render it useful. Such additions are costly, as are the facilities necessary to store the additional fluid.
As our invention is capable of concentrating and remediating any or all of the above described oil well fluids—brines, heavy brines, polymer-containing fluids, completion and workover fluids, drilling fluids, muds, and emulsions—we may refer to these collectively herein as “oil well fluids.” Similar fluids are used in the production of natural gas in gas wells, and accordingly we intend to include such fluids in the term oil well fluids. Oil well fluids generally may include high solids contents, but muds in particular may include solids commonly in the range of up to about 45% by volume. Such high solids content is detrimental to any conventional distillation process which might be considered to treat an oil field mud for recycling. Likewise emulsions are not conducive to conventional distillation as a separate procedure. Conventional distillation methods of concentrating dilute and particularly contaminated solutions including heavy brine components result in scaling and other difficulties which ultimately frustrate the economics of recycling. A more economical method is needed for recycling the components of oil well fluids.